Over the past two decades, there has been substantial activity in the development of various resin systems to lock mating threaded fasteners together against premature and unwanted disassembly, such as might be produced by vibration, impacts and the like. Although adhesives have been proposed for this purposes, the preferred resin systems are those which do not bond to the mating surfaces of the fastener members but which fill the spacing therebetween so as to produce signficant resistance to relative rotation and thereby disassembly.
Among the threadlocking compositions which are widely employed are the anaerobically curing acrylate resin materials of the type shown in Krieble U.S. Pat. Nos. 3,043,820 and 3,046,262. As is well known, such acrylate systems may require pretreatment of certain metal surfaces in order the achieve the desired result to avoid inhibition of the polymerization reaction; however, they do afford significant advantages in that curing will normally not commence until the composition has been removed from contact with air, thus providing extended pot life and/or working time.
Various curable resin systems have been suggested for threadlocking purposes as, for example, in Anthony U.S. Pat. No. 3,061,455; Schultz et al U.S. Pat. No. 3,179,143; Adams et al U.S. Pat. No. 3,396,116 and Deckert et al U.S. Pat. Nos. 3,642,937 and 3,746,068. The Schultz et al and the Deckert et al Patents are indicative of the efforts in the art to encapsulate the resin system components to extend their pot life and facilitate their use; the Anthony Patent provides reactive components on the opposed surfaces which mix upon assembly.
Epoxy resins offer significant economic advantages over the anaerobically curing acrylic systems because of their inherently lower cost, but problems have remained in that pretreatment of the fastener surfaces has frequently been required to achieve desired levels of torque to resist inadvertent disassembly. Moreover, some epoxy systems which would cure sufficiently rapidly to meet industrial needs have frequently suffered too short a pot life to permit practical use in many applications. Alternatively, relatively expensive apparatus has been developed for admixing the components of the epoxy system immediately prior to application.
As is well known, many fasteners used in industrial application retain on the surfaces thereof of film of organic material, most generally a lubricant used during the course of manufacture. It is known that such organic films decrease the effectiveness of the threadlocking compositions; it is believed that the organic material may inhibit proper polymerization. Heretofore, it has been considered necessary to pretreat the fasteners so as to remove all or substantially all of the interfering organic film prior to the assembly operation. Such operations obviously involve added costs and time. Exemplary of the prior art in this regard are Epstein et al U.S. Pat. No. 3,737,355 and Dobinson et al U.S. Pat. No. 3,746,685.
It is an object of the present invention to provide a novel epoxy threadlocking composition which may be used upon threaded fasteners without the necessity for pretreating such fasteners and which is rapidly curing to provide a desirable torque level for disassembly.
It is also an object to provide such an epoxy threadlocking composition which is relatively economical, relatively simple to compound and relatively trouble-free in use.